1. Field of the Invention
The present invention relates to a head chip that ejects liquid from a nozzle opening to record an image or a character on a recording medium, a liquid jet head including the head chip, and a liquid jet device including the liquid jet head.
2. Description of the Related Art
At present, as one example of a liquid jet device, there has been provided an ink jet type recording device that ejects ink (liquid) on a recording medium such as recording paper for recording an image, a character, or the like thereon. The recording device is, for example, a printer, a facsimile machine or the like. The recording device supplies ink to an ink jet head from an ink tank through an ink supply pipe, and ejects ink onto the recording medium from a nozzle opening of the ink jet head, thereby performing the recording.
In general, as illustrated in FIGS. 11 and 12, the ink jet head includes a head chip 100 including an actuator plate 101, a cover plate 102, a nozzle plate 103, and a support plate 104. In this example, the head chip 100 to which aqueous ink having an electrical conductivity is supplied is described.
The actuator plate 101 is a plate made of a piezoelectric material, and includes a plurality of grooves 111 each partitioned by side walls 110 therein. The grooves 111 function as channels into which ink flows to be accumulated. Plate-like drive electrodes (not shown) are formed on both side walls 110 of each groove 111 along the longitudinal direction thereof by vapor deposition or the like. A drive voltage is applied to the drive electrodes.
The cover plate 102 is stacked on the upper surface of the actuator plate 101, and blocks the plurality of grooves 111. An ink introduction aperture 102a into which ink is introduced is recessed in the cover plate 102. Further, slits 102b that communicate with the grooves 111 are formed in the ink introduction aperture 102a. In this situation, as illustrated in FIG. 13, the slits 102b alternately communicate with the grooves 111. As a result, the plurality of grooves 111 are in a state where grooves 111a to which ink is supplied and grooves 111b to which no ink is supplied are alternately arranged. The grooves 111a to which ink is supplied function as ejection channels, and the grooves 111b to which no ink is supplied function as dummy channels.
The actuator plate 101 and the cover plate 102 which are stacked on each other are supported by the support plate 104 in a state where those plates 101 and 102 are fitted into a fitting aperture 104a of the support plate 104 as illustrated in FIGS. 11 and 12. In this situation, an end surface of the support plate 104 is flush with end surfaces of the actuator plate 101 and the cover plate 102.
The nozzle plate 103 is in the form of a plate, and fixed to the end surfaces of the support plate 104, the actuator plate 101, and the cover plate 102 with an adhesive S. The adhesive S is omitted from FIGS. 11 and 12.
A plurality of nozzle openings 103a are formed at given intervals in the nozzle plate 103. In this situation, as illustrated in FIG. 13, the plurality of nozzle openings 103a are formed so as to communicate with the grooves 111a that function as the ejection channels. That is, the nozzle openings 103a are formed at the same intervals as those of the grooves 111a that function as the ejection channels.
When ink is ejected with the use of the ink jet head having the head chip 100 configured as described above, ink is first supplied to the inside of the grooves 111a that function as the ejection channels through the ink introduction aperture 102a and the slits 102b so that the grooves 111a are filled with the ink. Then, a drive voltage is applied to the drive electrodes. Then, due to the piezoelectric thickness-shear effect, the side walls 110 of the actuator plate 101 are so deformed as to project toward the grooves 111b being the dummy channels, and the volume of the grooves 111a being the ejection channels increases. With an increase in volume of the grooves 111a, ink is led to the grooves 111a from the ink introduction aperture 102a through the slits 102b. Then, after the ink has been led into the grooves 111a being the ejection channels, a drive voltage applied to the drive electrodes is set to zero, thereby returning the volume that has increased once to an original volume. Through the above-mentioned operation, a pressure inside of the grooves 111a being the ejection channels increases to pressurize ink.
As a result, a drop of ink, that is, an ink droplet can be ejected from the nozzle openings 103a. 
Incidentally, the nozzle plate 103 in which the plurality of nozzle openings 103a are formed is fixed with the adhesive S as described above. In general, in assembling the head chip 100, the nozzle plate 103 is attached onto the support plate 104, the actuator plate 101, and the cover plate 102 which are previously applied with the adhesive S. For that reason, in the attaching, the adhesive S is caused to flow into the nozzle openings 103a as illustrated in FIGS. 14 and 15, resulting in such a disadvantage that the nozzle openings 103a are partially infilled.
In particular, it is general that the nozzle openings 103a are each formed into a tapered configuration in cross section. For that reason, the inlet diameter of the nozzle openings 103a located on the grooves 111 side is larger than the outlet diameter thereof. Hence, the adhesive S is liable to flow into the nozzle openings 103a from the inlet side. When the inlet diameter of the nozzle openings 103a is larger than the horizontal width of the grooves 111, inflow of the adhesive S is particularly remarkable.
When a part of the nozzle openings 103a is thus blocked by inflow of the adhesive S, ejection failure in which, for example, ink cannot be normally ejected is induced. For that reason, it is desirable to take some countermeasures so as to prevent the above-mentioned disadvantages.
Under the circumstances, as one of the countermeasures, there is known a method of stepping the adhesive for adhesion of the nozzle plate (JP 05-330061 A). In the method, the nozzle openings are formed in the nozzle plate having an adhesive surface applied with the adhesive in advance. Then, the adhesive around the nozzle openings is concentrically removed with a diameter larger than the diameter of the nozzle openings.
As another countermeasure, there is known a method of forming a plurality of grooves for complementing a surplus of the adhesive around the nozzle openings when the nozzle openings are formed in the nozzle plate (JP 07-117230 A).
However, the conventional method still suffers from the following disadvantages.
First, according to the method of stepping the adhesive, it is conceivable to prevent the adhesive from flowing into the nozzle openings. However, it is difficult to find out a suitable adhesive for the stepping method. That is, the adhesive of this type is required to provide at least an adhesion property for firmly adhering to the nozzle plate, a shaping property for executing the stepping process, and ink resistance. However, it is difficult to actually find out the adhesive having those various properties, which makes the method unviable.
On the other hand, according to the method of forming a plurality of grooves for complementing a surplus of the adhesive around the nozzle openings, the surplus adhesive can be indeed pulled into the grooves. However, the adhesive applied at positions close to the nozzle openings is still caused to flow into the nozzle openings. Further, when the surplus adhesive fills the grooves, and the remaining surplus adhesive cannot be complemented by the grooves, the surplus adhesive is still caused to flow into the nozzle openings. For that reason, the amount of inflow adhesive may be indeed reduced, but inflow per se cannot be prevented. Accordingly, the possibility that the ejection failure is induced still remains.
Further, there is conceivable a technique in which, for the purpose of preventing the surplus adhesive from being contained, the adhesive having the amount smaller than the amount for sufficient adhesion is applied to allow the nozzle plate 103 to adhere to a joining body formed of the actuator plate 101 and the cover plate 102. However, when the above-mentioned technique is applied, there is the fear that the adhesion is insufficient. When the adhesion is insufficient, the following disadvantages may occur.
For example, in the case where the adhesion is insufficient, when the nozzle plate 103 is cleaned up by a cleaning member such as a wiper (not shown), there is a risk that the nozzle plate 103 may be peeled off from the above-mentioned joining body. Further, when the adhesion is insufficient, there is a risk that an unwanted gap may be formed between the nozzle plate 103 and the joining body, whereby the ink led to the ejecting groove 111 may leak out of the gap.
In this way, when the adhesive is insufficient, the fear may arise that the above-mentioned disadvantages occur. Therefore, it is essential to apply the sufficient amount of adhesive, and it is necessary to allow the nozzle plate 103 to surely adhere to the joining body. Accordingly, there arises the above-mentioned problem resulting from the adhesive